1. Field of the Invention
The present invention relates to an optical transmission device and optical module including a surface-type optical element and optical waveguide.
2. Description of the Related Art
Conventionally, an optical transmission device using a surface-type optical element in which a light emitting portion and a light receiving portion are formed on the back of a mounting face, such as a surface emitting laser (VCSEL) and photodiode, has been well known as a low cost optical transmission device (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 2004-226941, JP-A No. 2004-212774, JP-A No. 2003-329892, JP-A No. 11-271548, JP-A No. 05-093825, JP-A No. 10-227951, JP-A No. 11-119006, JP-A No. 08-330661, JP-A No. 05-224044, and JP-A No. 11-330624). Then, employment of the optical waveguide for optical coupling between an external optical transmission medium such as an optical fiber and the surface-type optical element has been considered for reduction of the size and cost and giving high functionality of the optical transmission device.
As for the mounting direction of the optical waveguide, it is possible to consider mounting the optical waveguide in parallel to the mounting face of the surface-type optical element and mounting it in a vertical direction thereto, and usually, a 45-degree plane 220 is formed in an optical waveguide 218 as shown in FIG. 26 from viewpoints of ease in holding and positioning and a surface-type optical element 222 is mounted such that a light emitting face 222L thereof is in parallel to the optical waveguide 218 (see JP-A No. 2004-226941).
However, this method requires processing of forming such 45-degree plane in the optical waveguide, whereby leading to increase in manufacturing cost and such a problem that a highly reliable package (for example, metal can package) which emit light vertically to the mounting face cannot be used.
As a method for mounting the optical waveguide vertically with respect to the mounting face of the optical element, a method of providing the optical waveguide with a concave portion and then positioning optically with this as a criterion has been proposed (see for example, JP-A No. 2004-212774).
However, this method has not only a weak point that the optical waveguide cost and mounting cost both increase but also a drawback that plural surface-type optical elements cannot be positioned to match with a single optical waveguide easily.